U.S. patent number 8,715,557 [Application Number 12/705,700] was granted by the patent office on 2014-05-06 for dimensional control of concrete blocks.
This patent grant is currently assigned to Anchor Wall Systems, Inc.. The grantee listed for this patent is Paul Joseph Johnson, Jimmie L. Mugge, Ronald J. Scherer, Paul Randal Tufts. Invention is credited to Paul Joseph Johnson, Jimmie L. Mugge, Ronald J. Scherer, Paul Randal Tufts.
United States Patent |
8,715,557 |
Johnson , et al. |
May 6, 2014 |
Dimensional control of concrete blocks
Abstract
A concrete block mold division plate for front-face-up block
molding. The division plate fits into a channel formed in each of
the side walls of the mold. A plurality of fasteners secure the
division plate within each channel and to the side walls of the
mold. The division plate operates in conjunction with an optimized
dry cast concrete mixture to provide acceptable control of the
flatness and parallelism of the top and bottom surfaces of the
blocks.
Inventors: |
Johnson; Paul Joseph
(Clearwater, MN), Mugge; Jimmie L. (Eagan, MN), Tufts;
Paul Randal (Eagan, MN), Scherer; Ronald J. (Stillwater,
MN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson; Paul Joseph
Mugge; Jimmie L.
Tufts; Paul Randal
Scherer; Ronald J. |
Clearwater
Eagan
Eagan
Stillwater |
MN
MN
MN
MN |
US
US
US
US |
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|
Assignee: |
Anchor Wall Systems, Inc.
(Minnetonka, MN)
|
Family
ID: |
37497894 |
Appl.
No.: |
12/705,700 |
Filed: |
February 15, 2010 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20100139200 A1 |
Jun 10, 2010 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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11195915 |
Aug 3, 2005 |
7674420 |
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Current U.S.
Class: |
264/336;
264/333 |
Current CPC
Class: |
B28B
7/241 (20130101); B28B 7/0044 (20130101) |
Current International
Class: |
B28B
7/10 (20060101) |
Field of
Search: |
;264/333,336 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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25 55 714 |
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Jun 1977 |
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DE |
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100 02 390 |
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Jul 2001 |
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DE |
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15740 |
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1913 |
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GB |
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244132 |
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Dec 1924 |
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GB |
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2 232 114 |
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Dec 1990 |
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GB |
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WO 03/060251 |
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Jul 2003 |
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WO |
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Other References
Bessert Parts & Equipment Catalog, pp. 5, 18-22. cited by
applicant .
International Search Report and Written Opinion for
PCT/US2006/028712, dated Dec. 28, 2006. cited by applicant.
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Primary Examiner: Hauth; Galen
Attorney, Agent or Firm: Merchant & Gould P.C.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. patent application Ser.
No. 11/195,915, filed Aug. 3, 2005, which application is hereby
incorporated by reference in its entirety.
Claims
What is claimed is:
1. A process for manufacturing dry cast concrete wall blocks front
face up; the wall blocks, with respect to orientation in a wall,
having the front face molded with a predetermined three-dimensional
pattern, an opposite rear face, top and bottom opposite faces
extending between the front and rear faces, and side faces
extending between the front and rear faces and the top and bottom
faces; the process comprising the steps of: molding a concrete wall
block by depositing a dry cast concrete mixture comprising at least
13.5%, by weight, cementitious material content into a mold; the
mold being positioned upright and having two mold sidewalls and two
mold end walls; the upright mold having an open top and an open
bottom; the upright mold being positioned on a pallet so that the
open bottom is closed by the pallet; the mold further having at
least a first division plate having a bottom region, side regions,
an upper region, and face regions; the first division plate
extending from the open top of the mold to the open bottom of the
mold; the side regions of the first division plate defining a first
side edge and an opposite second side edge; forming the concrete
wall block side faces by compacting the dry cast concrete mixture
against the mold sidewalls; forming the concrete wall block rear
face by compacting the dry cast concrete mixture against the
pallet; forming one of the concrete wall block top or bottom face
by compacting the dry cast concrete mixture against one of the face
regions of the first division plate that is rigidly constrained
during operation of the process; the two mold sidewalls each having
a vertical surface from the open bottom of the mold to the open top
of the mold; each of the two mold sidewalls having a vertical
channel therein along a substantial entirety of the vertical
surface from the open bottom of the mold to the open top of the
mold; the vertical channel in each sidewall being parallel to the
other and generally perpendicular to the open top and open bottom
of the mold; the first division plate having a portion slidably
received in the mold with the first edge received in a first one of
the vertical channels and with the second side edge received in a
second one of the vertical channels; the first side edge being
rigidly constrained within the first vertical channel, against
movement during molding, by securement in addition to the first
vertical channel; the second side edge being rigidly constrained
within the second vertical channel, against movement, by securement
in addition to the second vertical channel; and forming the other
top or bottom face of the concrete wall block by compacting the dry
cast concrete mixture against a face region of a wall or plate that
is opposite to the first division plate and that extends to the
open bottom of the mold; forming the concrete wall block front face
by compacting the dry cast concrete mixture with a stripper shoe in
the open top of the mold to impart a predetermined
three-dimensional pattern to the concrete wall block front face;
the predetermined three-dimensional pattern having a relief, in at
least a portion thereof, of at least about 0.5 inch; stripping the
concrete wall block from the open bottom of the mold onto the
pallet; and curing the concrete wall block to result in a cured
concrete wall block.
2. A process according to claim 1 wherein: the first side edge is
rigidly constrained by at least one bolt; and, the second side edge
is rigidly constrained by at least one bolt.
3. A process according to claim 2 wherein: the first side edge is
rigidly constrained by at least one bolt extending through a first
mold sidewall; and, the second side edge is rigidly constrained by
at least one bolt extending through the second mold sidewall.
4. A process according to claim 3 wherein: the first side edge is
rigidly constrained by at least one bolt engaging the first side
edge; and, the second side edge is rigidly constrained by at least
one bolt engaging the second side edge.
5. A process according to claim 4 wherein: the first side edge is
rigidly constrained by two bolts engaging the first side edge; and,
the second side edge is rigidly constrained by two bolts engaging
the second side edge.
6. A process according to claim 1 wherein: the first side is
rigidly constrained in the first vertical channel at two vertically
spaced locations; and, the second side is rigidly constrained in
the second vertical channel at two vertically spaced locations.
7. The process of claim 1 wherein: the step of forming one of the
concrete wall block top or bottom face includes compacting the dry
cast concrete mixture against a face region of a first division
plate in which the clearance between the side edges of the first
division plate and each of the channels is no greater than 0.013
inches.
8. The process of claim 1 wherein: the step of forming the other
top or bottom face of the concrete wall block includes compacting
the dry cast concrete mixture against a face region of a second
division plate that is opposite the first division plate; the
second division plate having opposite side edges slideably received
in, and rigidly constrained in, a channel in each of the mold
sidewalls holding the side edges of the second division plate; each
of the channels holding the second division plate being parallel to
each other and generally perpendicular to the open top and open
bottom of the mold; the opposite side edges of the second division
plate each being rigidly constrained in an associated one of the
channels; the second division plate extending to the open bottom of
the mold.
9. The process of claim 1 wherein: the first division plate has
protrusions extending away from the side edges; the protrusions
having a plurality of bolt holes; the side edges having a plurality
of bolt holes; the two mold side walls each having a vertical
surface and a horizontal flange at an upper region of the mold side
walls; the vertical surface of each mold side wall defining the
channels; the horizontal flange of each of the mold side walls
having a plurality of bolt holes, and the channels of each mold
side wall having a plurality of bolt holes; the step of forming one
of the concrete wall block top or bottom face includes compacting
the dry cast concrete mixture against a face region of a first
division plate that is rigidly constrained by: (i) the plurality of
bolts extending through the bolt holes of the mold side wall
channels and the bolt holes in the side edges of the first division
plate; and (ii) a plurality of bolts extending through the bolt
holes of each of the mold side walls horizontal flange and the bolt
holes of the first division plate protrusions.
10. The process of claim 1 wherein the cured concrete block has a
top and bottom face that have less than 1/32 of an inch deviation
in flatness and parallelism.
11. The process of claim 1 wherein the block is a retaining wall
block.
Description
FIELD OF THE INVENTION
The invention relates generally to the manufacture of concrete
blocks. More specifically, the invention relates to dimensional
control of the top and bottom surfaces of concrete blocks that are
formed front face-up in a mold for use in mortar-less walls.
BACKGROUND OF THE INVENTION
Modern, high speed, automated concrete block plants and concrete
paver plants make use of concrete block molds that are open at the
top and bottom. These molds are mounted in machines which
cyclically station a pallet below the mold to close the bottom of
the mold, deliver dry cast concrete into the mold through the open
top of the mold, densify and compact the concrete by a combination
of vibration and pressure, and strip the uncured blocks from the
mold by a relative vertical movement of the mold and the
pallet.
For efficient high-volume production, concrete block molds are
typically configured to produce multiple blocks simultaneously. A
concrete block mold generally comprises side walls and end walls
that define the periphery of a mold cavity. Within this mold
cavity, division plates may be used to sub-divide the mold cavity
into a plurality of block-forming cavities. Further, movable side
walls may be used to form the side faces of the block-forming
cavity. The division plates are generally rectangular-shaped plates
attached to the side walls of the mold. Further, the side walls of
the block cavity and the division plates may be covered with
replaceable mold face linings to protect the mold components from
abrasive wear.
As disclosed in U.S. Published Patent Application 20030182011, some
blocks are now being formed with patterned or other processed front
faces while retaining the high-speed, mass production of the
blocks. As disclosed in U.S. Published Patent Application
20030182011, the blocks can be formed front face-up in the mold,
allowing the front face of the block to be contacted by a stripper
shoe which imparts a desired three-dimensional pattern to the front
face. When a block is formed front-face-up in the mold, the top and
bottom surfaces of the blocks (from the perspective of the block as
laid in a wall) are formed by division plates. Because the side
surfaces of a block must converge to allow the blocks to be laid up
in a curved or radiused wall, the front of the block is typically
wider than the rear of the block. In order for a block formed
front-face-up to be discharged through the bottom of the mold, the
side surfaces of a block must be formed by movable side walls that,
in a first position during molding, form the wider front portion
and narrower bottom portion of the block, and in a second position
during discharge of the block from the mold, move sufficiently out
of the way for the wider front portion of the block to pass through
the bottom of the mold.
A problem that arises when blocks are formed front-face-up in a
conventional block mold is that the blocks are prone to being
formed with the top and bottom surfaces not being flat and parallel
to each other. Since concrete retaining wall blocks are typically
assembled without mortar, there is little ability to accommodate
variations in the flatness and parallelism of the top and bottom
surfaces during the assembly of a wall. It is very important,
therefore, that the top and bottom surfaces of the blocks that
engage with other blocks be formed as flat as possible and parallel
to each other to allow the blocks to lay flat and level on blocks
in a lower course of blocks, as well as to allow blocks in an upper
course to lay flat and level.
It is also important during the commercial manufacture of concrete
blocks that the manufacturing expenses be minimized. Certain
components in the concrete mixture are more expensive, such that
increasing the percentage of those components in the concrete
mixture increases the manufacturing expense. In particular,
cementitious materials are a component of a concrete mixture that
is typically more expensive than other components. However, the
percentage of cementitious materials in the concrete mixture
affects the stability and dimensional control of the resulting
concrete block. Therefore, it is desired to minimize the amount of
cementitious material required in the concrete block mixture while
still maintaining acceptable block properties and dimensional
control.
Thus, there is a demand for concrete block manufacturing processes
that provide for improved control of the flatness and parallelism
of the top and bottom surfaces of concrete blocks formed front
face-up in a mold, while minimizing the expense of the concrete
mixture.
SUMMARY OF THE INVENTION
An improved concrete block manufacturing process provides for
improved control of the flatness and parallelism of the top and
bottom surfaces of concrete blocks formed front face-up in a mold.
The improved manufacturing process incorporates an improved
concrete block mold and a modified concrete mixture that operates
in cooperation with the concrete block mold. A concrete block mold
is provided with a division plate that is secured in the mold in a
manner that allows the block to be formed with close control of the
top and bottom surfaces. The division plate is secured within
channels formed in the side walls of the mold that extend
substantially the entire height of the mold cavity so that
substantially the entire height of the division plate is secured in
the channels, without interfering with the pivoting side wall
mechanism. The channels are sized so that there is minimal play
between the side edges of the division plate and the channels. A
plurality of fasteners secure the division plates to the side walls
of the mold. The concrete block mold allows for the use of a
concrete mixture with an optimized content of cementitious
material, sand, coarse aggregates, and water, where the content of
cementitious material is minimized. The concrete mixture is
optimized to work in conjunction with the mold, so as to provide a
block with sufficient stability prior to being cured that the block
adequately retains the geometry formed within the mold.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view showing the bottom, front, and one
side of a concrete block produced according to the present
invention.
FIG. 2 is a top view of a concrete block mold according to the
present invention.
FIG. 3 is a cross-sectional view of the concrete block mold taken
along line A-A of FIG. 2.
FIG. 4 is a cross-sectional view of a division plate according to
the present invention.
FIG. 5 is a perspective view of a portion of a mold side wall for
the concrete block mold of FIG. 2.
FIG. 6 is a cross-sectional view of a concrete block mold taken
along line B-B in FIG. 2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention provides a division plate for a concrete
block mold. The resulting surface that is shaped by the division
plate is substantially flat, which aids in the construction of a
high quality wall or other structure made from a plurality of the
concrete blocks.
The division plate works in concert with an optimized concrete
mixture to provide the desired control of the block geometry. The
concrete mixture generally comprises coarse aggregate, sand (also
called fine aggregate), cementitious material, colorant (also
called pigment), and water. The concrete mixture can be made more
stable and self-supporting by increasing the content of coarse
aggregate material. However, a greater concentration of coarse
aggregate material may prevent the formation of fine detail on the
front face of the block, which is often desired when forming blocks
front-face-up. Similarly, the concrete mixture can also generally
be made more stable by increasing the amount of cementitious
material in the concrete mixture, within limits. This helps to
prevent the block from slumping after being released from the mold
and before being cured. However, cementitious material is
relatively expensive and therefore it is desired to keep its use to
a minimum. Further, increased percentages of cementitious material
may make the concrete mixture stickier, which can prevent the
concrete mixture from flowing into the mold properly. The present
invention allows the use of a concrete mixture that is optimized
for sufficient block stability without unnecessarily increasing the
expense of the mixture, making the mixture too sticky to flow into
the mold, or preventing the formation of sufficient detail on the
front face of the blocks.
The invention will be described with respect to the formation of
retaining wall blocks front-face-up in a mold as disclosed in U.S.
Published Patent Application 20030182011, which is incorporated
herein by reference in its entirety. In such a front-face-up
orientation, the top and bottom surfaces of the blocks are formed
by division plates (or by one division plate and one end of the
mold in the outer cavities of the mold). In addition, the division
plate that forms the lower surface of the block may be provided
with an undercut at the open bottom of the mold in order to form a
locator protrusion, for example a flange, as disclosed in U.S.
Published Patent Application 20030182011. However, the inventive
concepts could be applied to the formation of other blocks in other
orientations.
The formation of blocks with top and bottom surfaces that are not
flat and parallel is an especially significant problem because it
may prevent the block from laying flat or preventing other blocks
from laying flat on the block when laid up in a wall. It has been
determined that 1/32 of an inch deviation in flatness and
parallelism is a suitable maximum value of deviation. Preferably,
the production process results in most blocks having less than 1/32
of an inch deviation in flatness and parallelism and only a few
having the maximum of 1/32 of an inch deviation. Although a maximum
deviation of less than 1/32 of an inch may be desirable, the
additional expense and difficulty of further reducing this
deviation may not be justified.
A concrete block produced according to the present invention is
illustrated in FIG. 1. The block 80 comprises a block body having a
front face 82, a rear face 84, a top face 86, a bottom face 88, and
opposed side faces 90, 92. (Note that the terms front, rear, top,
bottom, and side faces reference the orientation of the faces of
the block as placed within a wall and do not necessarily reflect
the orientation of the block as it is produced. Block 80 is shown
in FIG. 1 in a generally bottom-face-up orientation to show the
features of the block, but such orientation is not representative
of the orientation of the block as placed within a wall.) The front
face 82 is provided with a predetermined three-dimensional pattern,
as described in U.S. Published Patent Application 20030182011.
Block 80 also preferably includes a flange 94 that extends below
the bottom face 88 of the block. When a retaining wall is
constructed using a plurality of blocks 80, flange 94 of a block 80
is designed to abut against the rear face 84 of a block in the
course below the block to provide a pre-determined set-back from
the course below and to provide course-to-course shear
strength.
With reference to FIG. 2, a concrete retaining wall block mold 20
is illustrated as comprising a generally rectangular structure
defining a mold cavity, where both the top and bottom of the mold
cavity are open. The rectangular structure is generally defined by
two mold side walls 22 and two mold end walls 24. The mold cavity
is further divided into a plurality of individual block-forming
cavities 28 by a plurality of division plates 26. Division plates
26 and block cavity movable side walls 18 together define the
individual block forming cavities 28 (except at the cavities at the
ends of the mold 20, where a mold end wall 24 defines one surface
of the individual block-forming cavity). During block formation,
the open bottom of the mold and each block-forming cavity 28 is
closed by a pallet that is moved into place under the mold 20. The
top of the mold is open to allow dry cast concrete to be deposited
into the cavities 28, after which stripper shoes connected to a
compression head are brought into contact with the concrete within
the cavities 28.
The mold 20 is constructed so that the blocks are formed
front-face-up (i.e. with the front faces facing upward) and the
rear faces supported on the pallet positioned underneath the mold
20. Further information on front face-up block formation can be
found in U.S. Published Patent Application 20030182011. In this
orientation, the top and bottom surfaces of the block are formed by
two adjacent division plates 26, or by a division plate 26 and a
mold end wall 24. Referring to FIG. 3, the side faces of the block
are typically formed by movable side walls 18 that, when in a first
position during the molding stage, form the converging sides of the
block, and when pivoted to a second position during the discharge
stage, are retracted to allow the block to be discharged from the
bottom of the mold. The position of the block cavity movable side
walls 18 may be controlled by a mechanism such as a camshaft 16.
However, other devices may be used as disclosed in U.S. Published
Patent Application 20030182011. The blocks are discharged through
the bottoms of the cavities 28 by relative vertical movement of the
pallet and mold 20. The stripper shoes attached to the compression
head or head assembly help push the blocks out of the cavities
28.
Oftentimes, the block forming surfaces of the mold cavities 28 are
provided with replaceable wear liners that actually contact the
concrete in the mold cavities. These liners help prevent wear on
the division plates 26, block cavity movable side walls 18, and
mold end walls 24, which tend to be expensive to replace. The use
of wear liners is known to those having ordinary skill in the art.
Therefore, although not illustrated in the drawings, references to
the block cavity movable side walls 18, mold end walls 24, and
division plates 26 as forming faces of the blocks is meant to
include direct formation of the faces by the block cavity movable
side walls 18, mold end walls 24, and plates 26, as well as
formation of the faces by wear liners attached to the block cavity
movable side walls 18, mold end walls 24, and plates 26.
Referring to FIG. 4, a division plate 26 according to the present
disclosure comprises a plate having a bottom region 30, an upper
region 32, side regions 34, and face regions 36. The division plate
26 also comprises a plurality of threaded bolt receiving holes 38
that extend into the division plate through side regions 34. Upper
region 32 is characterized by protrusions 60 that extend away from
side regions 34 and that typically contain a plurality of bolt
clearance holes 62. Bottom region 30 is characterized as having
cut-outs 64 along side regions 34 that provide clearance for the
mechanism of the movable side wall. Cut-outs 64 are preferably as
small as necessary to provide clearance for the movable side wall
mechanism and typically constitute about one-quarter of the height
of the division plate.
Referring now to FIG. 5, an embodiment of a segment of one of the
mold side walls 22 is shown. The other mold side wall is a mirror
image of identical construction. The mold side wall 22 comprises a
vertical surface 40 and a horizontal flange 42 protruding away from
the mold cavities 28 at the upper region of mold side wall 22. In
addition, a channel 44 is formed along the substantial entirety of
the height of the vertical surface 40. The channel 44 is configured
to receive the edge of the side region 34 of the division plate 26
as shown in FIG. 6. It is very important that each of the channels
44 in the mold side wall 22 be parallel to each other and square to
the top and bottom of the mold. The channel 44 is sized to receive
the edge 34 of the division plate 26 with minimal play (clearance)
between the channel 44 and plate 26 in order to minimize the amount
of movement of the plate 26. For example, for a plate 26 having a
thickness range, with manufacturing tolerances, of about 1.245 to
1.250 inches (31.623 to 31.750 mm), the channel 44 can have a width
range, with manufacturing tolerances, of about 1.250 to 1.258
inches (31.750 to 31.953 mm). The clearance between the plate 26
and the channel 44 can therefore range between about 0.000 to 0.013
inches (0.000 to 0.330 mm). The channel is preferably, with
manufacturing tolerances, about 0.307 to 0.312 inches deep (7.80 to
7.92 mm). A plurality of bolt clearance holes 46 extend through
mold side wall 22 within channel 44. Also, a plurality of bolt
holes 47 extend through horizontal flange 42.
FIG. 6 shows a cross section of a division plate 26 assembled to
the mold side wall 22 within the mold 20, taken along line B-B in
FIG. 2. The edges 34 of the division plate 26 are disposed in close
fitting relation with the channels 44 in the mold side wall 22.
Bolts 48 that extend through the bolt holes 38 and bolt holes 46
further secure the division plate 26 to the mold side wall 22.
Additionally, bolts 49 extend through bolt holes 62 and into bolt
holes 47 to provide additional securement of the division plate 26
to the mold side wall 22. Accordingly, division plate 26 is rigidly
constrained during the block molding operation.
The concrete mixture is also an important part of controlling the
dimensions of concrete blocks. In forming blocks from dry-cast
concrete, the blocks are formed in a mold, removed from the mold,
transported to a storage location, and then cured. Thus, when the
blocks are removed from the mold they are not yet cured. It is
therefore important that the blocks have sufficient stability and
rigidity that they can support their own weight until they are
cured, without slumping or losing their shape.
A typical concrete mixture comprises cementitious material, sand,
coarse aggregates, colorants, and water. Cementitious materials may
include such materials as cement, fly ash, slag, silica fume, and
other pozzolans, and the methods of properly selecting or combining
these constituents are known to those of skill in the art. It is
possible to increase the stability of the blocks after they are
removed from the mold by increasing the size of the coarse
aggregates in the concrete mixture or by increasing the percentage
of the mixture consisting of coarse aggregates. Coarse aggregates
are a collection of rocky materials that have typically been
screened or otherwise mechanically separated, such as by a sieve,
to produce a coarse aggregate size distribution that comprises
material of a maximum size (typically determined by the size of the
openings in the screen or sieve) and smaller materials. For
example, the coarse aggregate component may comprise a mixture of
aggregates with a characteristic size of 3/16 inch or 1/4 inch.
Increasing the size of the coarse aggregates or increasing the
percentage of the coarse aggregates within the mixture creates a
coarser mixture. While a coarser mixture may improve the stability
of the block after it is removed from the mold, the coarser mixture
may not be desirable because it may prevent the formation of a high
level of detail on the front face of the block.
Generally, increasing the content of cementitious material in the
mixture will also increase the stability of the blocks after they
are removed from the mold. However, at some point, such as about 21
percent cementitious material in the concrete mixture, increasing
the amount of cementitious material will not increase the stability
of the blocks after they are removed from the mold, and may in fact
decrease the stability of the blocks. However, a typical concrete
mixture contains around 12 percent cementitious material, such that
increases in the amount of cementitious material generally increase
the stability of the blocks after they are removed from the mold.
Increasing the content of cementitious material in the mixture has
the further advantage that it will not limit the amount of detail
that can be formed on the front face of the block. However,
increasing the content of cementitious material in the mixture will
make the mixture more expensive. Additionally, increasing the
content of cementitious material will make the mixture stickier,
which makes it more difficult to completely and consistently fill
the mold cavity. Where greater amounts of cementitious material are
used, it may be necessary to add larger amounts of water to the
mixture to allow the mixture to flow properly. However, increased
quantities of water may tend to reduce the stability of the blocks
after they leave the mold. Therefore, determination of the mixture
composition is both difficult and critical.
The mold with the division plates of the present invention allows
the blocks to be suitably formed with an acceptable concrete
mixture. The inventors have determined that the following concrete
mixture yields good results when used in conjunction with the mold
and division plates of the present disclosure:
TABLE-US-00001 Component Weight (dry) Percentage of total Coarse
aggregate ( 3/16 458 lbs. 9.0% inch) Sand 3,642 lbs. 71.5%
Cementitious material 700 lbs. 13.7% Colorant 36 lbs 0.7% Water 261
lbs 5.1% Total for Batch 5097 lbs 100%
It is generally desired to minimize the content of cementitious
material in order to minimize costs. A cementitious material
content of about 13.5 percent is the minimum that will function
properly in accordance with the present disclosure. Although it is
generally desirable to use the minimum content of cementitious
material, a cementitious material content of 15 percent will still
yield acceptable results.
A typical concrete mixture for blocks formed conventionally
according to methods known to those of skill in the art may contain
around 12 percent cementitious material. When blocks are formed
front-face-up according to the methods described in U.S. Published
Patent Application 20030182011, they are more prone to having
excessive deviations of the upper and lower face flatness, and as
such, may require greater amounts of cementitous material to yield
acceptable properties when used with molds with standard division
plates. However, the use of the division plates of the present
invention allows the use of an optimized concrete mixture with only
about 13.5 to 15 percent cementitious material while maintaining
adequate block geometry. Thus, the division plates of the present
invention allow for a substantial reduction in cementitious
material content in the concrete mixture, and thereby results in
substantial cost savings.
* * * * *